1. Field of the Invention
The present invention relates to an organopolysiloxane composition which generates a cured product via an organopolysiloxane addition reaction, and is particularly useful for protecting ICs and hybrid ICs, and sealing power modules and the like.
2. Description of the Prior Art
Silicone gels and silicone potting materials are addition reaction curable organopolysiloxane compositions which comprise an organohydrogenpolysiloxane containing hydrogen atoms bonded to silicon atoms (namely, SiH groups), an organopolysiloxane containing alkenyl groups such as vinyl groups bonded to silicon atoms, and a platinum-based catalyst, and which yield a cured product via an addition reaction of the SiH groups to the vinyl groups or other alkenyl groups. These silicone gels and silicone potting materials display excellent levels of heat resistance, weather resistance, oil resistance, low-temperature resistance, and electrical insulation, and also display low elastic modulus values and low levels of stress, and as a result, they are widely used in the protection of vehicle-mounted electronic components and household electronic appliance components (patent reference 1). In recent years, due to decreases in the heat resistant temperature of electronic components and the heat resistant temperature of substrates and casings used for mounting such electronic components, and decreases in the internal thermal stress caused by the difference between the temperature during curing and the temperature during use, reductions in the curing temperature for silicone materials to temperatures below conventional levels are now being sought. Moreover, shorter curing times are also being demanded. In addition, from the viewpoint of workability, one-part compositions are preferred to two-part compositions. However, it is well known that reducing the curing temperature and enabling shorter curing times causes a marked deterioration in the storage characteristics of one-part compositions. Moreover, it is also known that low temperature curing promotes wrinkling of the surface of the silicone cured product.
Typically known methods for improving the storage characteristics of a one-part composition include increasing the quantity of reaction retarding agent, or altering the nature of the reaction retarding agent, but when either of these methods is adopted, curing at low temperature becomes impossible. Low temperature curing can be achieved by using a reaction retarding agent with a comparatively low boiling point, but this can cause a deterioration in the storage characteristics of the one-part composition, as well as increasing the likelihood of wrinkling occurring on the surface of the cured product during curing, and increasing the danger of a deterioration in the durability of a product filled with the silicone composition.
Accordingly, the development of a curable organopolysiloxane composition that is capable of resolving the above problems, whether used as a one-part composition or as a two-part (or greater) composition, has been keenly sought.
[Patent Reference 1]
US Patent Publication No. 2002/0016019A